Diagnosing lack of top-end power

MongooseGA · 10-31-2013, 10:08 PM

I searched and didn't find a whole lot. I'll try to keep this short.

I've been able to drive my 3.0 swapped 911s pretty regularly for the first time in nearly a year.

Tonight I took the 911 out for dinner and drinks with my fiancee. I was crusing in 5th at maybe 60 MPH and needed to pass someone. I decided I'd have a little fun and dropped her into 3rd. Aside from the difficulty finding the gear (I attribute this to being a clunky 915?), once it was in gear all I got was extra engine noise. No real significant pull.

Tonight was the first time I've had it on the highway recently. I remember before she was down that top-end power was at least adequate. While down she got new plugs, magnacore wires, MSD ignition (still need the tach adapter), Brad Penn oil, new air filter, yadda yadda. All signs should point to more power everywhere.

What should I be looking for here? I'm feeling pretty lackluster about the car after tonight's drive. My fiancee also complained about a pretty noticeable burning smell. Could have been oil smoke coming from the heat exchangers or hot rubber from some fender rubbing, but I couldn't quite tell.

snbush67 · snbush67's Garage

Did the engine spin up in RPMs but you weren't propelled forward at warp speed? You probably smelled your clutch burning.

It happens...you may have just pressed on the accelerator before releasing the clutch all the way.

MongooseGA · 10-31-2013, 11:04 PM

Quote:

Originally Posted by snbush67

Did the engine spin up in RPMs but you weren't propelled forward at warp speed? You probably smelled your clutch burning.

It happens...you may have just pressed on the accelerator before releasing the clutch all the way.

Clutch fully let out, gas pedal to the floor. It may be possible it was clutch, but I doubt it.

I have a suspicion that my accelerator isn't allowed full travel due to the carpeting in the car; however, this is pretty much negated by the fact that the engine pulls so strongly in lower gears. There seems to be plenty of fuel input down low.

Is it possible I have some funky gearing in the car?

Nostril Cheese · 11-01-2013, 12:32 AM

Based on your description, I'd also guess a slipping clutch.

You say it's a 3.0. Does it have the original CIS? Is there fresh gas in the car?

MongooseGA · 11-01-2013, 04:21 AM

Fresh gas. CIS as well.

I don't know what happened, but today I did the same thing on the way to work and she pulled very well. Could be a slipping clutch? Would that be intermittent?

r-mm · 11-01-2013, 05:17 AM

Could it be a non-existant turbocharger causing the problem?

Norm Faustino · Norm Faustino's Garage

Get it up to highway speed in 5th and downshift it to 4th (not violently) but let the clutch pedal out with a bit of a snap. If the rpms show little to no increase you have a high load slip in the clutch. in other words it slips under high gear conditions but may not show up so much under lighter loads such as gears 1 thru 3. That is my contribution hope it helps isolate the clutch as a culprit.

MongooseGA · 11-01-2013, 09:26 AM

Quote:

Originally Posted by r-mm

Could it be a non-existant turbocharger causing the problem?

Haha, I believe this may be the case!

Norm- What you're describing sounds very similar to what I'm experiencing. Is your diagnosis the tell-tale sign of a clutch soon to be completely shot? The smell we noticed the other night has come around a few times this week, and I've noticed it mainly after going through high RPMs. I supposed it could be the clutch; I've not really had an issue with burning clutches before.

Norm Faustino · Norm Faustino's Garage

My cyber-diagnosis let's call it, if your clutch is in fact, behaving like you said, can only mean that it will worsen and stop clutching altogether. If you live in hilly terrain where the loads change constantly or an area prone to stop and go commutes, I wouldn't chance it much longer. If you wind up changing it I would recommend doing the typical complimentary repairs such as a main seal change and maybe a new release fork. Metal fatigue is the silent killer here. And by killer I mean of the part, not you. Good luck buddy.

emac · emac's Garage

No doubt the clutch.

snbush67 · snbush67's Garage

You might just need a cable adjustment. If it is an intermittent issue that only occurrs after dinner and drinks while trying to impress the ladies, then try by cutting out one of the three, in order of your priorities.

MongooseGA · 04:50 PM

Quote:

Originally Posted by snbush67

You might just need a cable adjustment. If it is an intermittent issue that only occurrs after dinner and drinks while trying to impress the ladies, then try by cutting out one of the three, in order of your priorities.

After reading the process of replacing the clutch, which is way over my head at this point, I hope you may be right.

Just for the record, the slipping was before the dinner. And my fiancee was hardly amused. When I tried duplicating the issue today the car pulled fine. I have not been on the highway this evening due to some bad weather here.

snbush67 · snbush67's Garage

Ha! Well at least check the cable for proper set up. Just for the record I have spun my clutch a few times but it's still holding strong. I wouldn't be overly worried about it.